The radiometer has been regarded since the 19th Century as a scientific novelty. Invented by Sir William Crooks, the radiometer generally consists of a set of vanes contained within a glass bulb. When forms of light (photons) hit the vanes, the radiation effect on the vanes causes them to move. This means that if the vanes are mounted between two needles, the vanes will rotate. This effect is attributed to light or radiation particles hitting a polished side of the vanes, which are contained within a partial vacuum.
Various modern versions of the radiometer include the Nichols radiometer and other microwave and gas radiometers. However, much of the same principles are involved as radiation, gas or light slams into specific sides of the vanes to cause them to rotate. Other variations include having the vanes absorb radiation so as to detect levels of radiation in the specific environment or scenario. But it should be noted that the principles of the radiometer tend to relate to low level scientific testing or novelty.